Due to their desirable physical properties such as strength and toughness (i.e., the combination of elongation and impact strength), rubber-reinforced polymer resins derived from styrene, or derivatives of styrene, and optionally, one or more comonomers, are employed in a variety of commercial applications such as packaging, refrigerator linings, furniture, casings for domestic appliances and toys. The rubber-reinforced, styrenic polymer resins generally comprise discrete particles of rubber, e.g., cross-linked polybutadiene or a block copolymer of butadiene and styrene, dispersed throughout a polymer matrix of styrene (conventionally referred to as high impact polystyrene or HIPS) or a polymer matrix of a copolymer of styrene and acrylonitrile (conventionally referred to as ABS).
Due to the physical property requirements of many end-use applications, it is often desirable to increase the physical properties, such as the heat distortion temperature and tensile properties, of the rubber-reinforced resins. It is known that the high temperatue properties as well as the tensile properties of the rubber-reinforced styrenic polymer resins can be improved by incorporating a mineral fiber such as chopped glass fiber in the resin product. Unfortunately, the enhanced tensile and high temperature properties imparted to the styrenic resin by the glass fibers or other mineral fibers are typically accompanied by a coincident and significant reduction in impact strength. This reduction in impact strength is particularly evident when the glass fiber is employed to reinforce a rubber-reinforced styrenic polymer resin.
In view of this stated deficiency in the polymeric resin products of the prior art reinforced with a mineral fiber, it remains highly desirable to provide a styrenic polymer resin reinforced with a mineral filler which mineral reinforced resin exhibits an improved balance of physical properties.